Increase in tendon protein synthesis in response to insulin-like growth factor-I is preserved in elderly men

Rie Harboe Nielsen, Lars Holm, Nikolaj Mølkjær Malmgaard-Clausen, Søren Reitelseder, Katja Maria Heinemeier, Michael Kjaer

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18 Citations (Scopus)


Insulin-like growth factor-I (IGF-I) is known to be an anabolic factor in tendon, and the systemic levels are reduced with aging. However, it is uncertain how tendon fibroblasts are involved in tendon aging and how aging cells respond to IGF-I. The purpose of this study was to investigate the in vivo IGF-I stimulation of tendon protein synthesis in elderly compared with young men. We injected IGF-I in the patellar tendons of young (n = 11, 20-30 yr of age) and old (n = 11, 66-75 yr of age) men, and the acute fractional synthesis rate (FSR) of tendon protein was measured with the stable isotope technique and compared with the contralateral side (injected with saline as control). We found that tendons injected with IGF-I had significantly higher protein FSR compared with controls (old group: 0.018 ± 0.015 vs. 0.008 ± 0.008, young group: 0.016 ± 0.009 vs. 0.009 ± 0.006%/h, mean ± SE, P <0.01). This increase in protein synthesis was seen in both young and old men, with no differences between age groups. The old group had markedly lower serum IGF-I levels compared with young (165 ± 17 vs. 281 ± 27 ng/ml, P <0.01). In conclusion, local IGF-I stimulated tendon protein synthesis in both young and old men, despite lower systemic IGF-I levels in the old group. This could indicate that the changed phenotype in aging tendon is not caused by decreased fibroblast function.
Original languageEnglish
Pages (from-to)42-46
Number of pages5
JournalJournal of Applied Physiology
Issue number1
Early online date21 Nov 2013
Publication statusPublished - 1 Jan 2014


  • Adult
  • Aged
  • Aging
  • Fibroblasts
  • Humans
  • Insulin-Like Growth Factor I
  • Male
  • Patellar Ligament
  • Protein Biosynthesis
  • Young Adult
  • growth hormone
  • protein turnover
  • tenocytes
  • growth factors


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